Forty years after the introduction of the 1971 Misuse of Drugs Act, more than 2.8 million people report using illicit drugs every year in England and Wales. While cannabis remains overwhelmingly the most popular, this Home Office total also includes 800,000 mainly young adults who put the country at the top of the European league table for powder cocaine use.

There are a further 300,000 people regularly using heroin, crack cocaine or other opiates who are officially described as "problem drug users".

The latest Ministry of Justice figures, published last week, show that 79,413 people were found guilty of, or given a formal caution – and therefore a criminal record – for possession of a controlled drug in 2010.

They included 44,058 people who were arrested and found guilty of possessing cannabis, of whom 18,870 were cautioned. A further 11,000 people were criminalised for simple possession of other class B and class C drugs such as amphetamines and tranquillisers. A total of 23,648 were found guilty of possessing class A drugs, which includes cocaine and ecstasy. A total of 1,400 were jailed last year for simply possessing illegal drugs, including 60 for cannabis possession. More than a quarter of those convicted at court for a possession offence were aged under 21.

The confused recent political history of the laws on cannabis possession, combined with continuing police discretion, means that a two-tier system remains in force. So while 44,000 people were dealt with in court for cannabis possession in 2010, a further 79,107 received informal warnings and 13,916 were given fixed a penalty notice – neither of which result in a criminal record.

Much was made of the alleged damage caused by David Blunkett's decision in 2004 to downgrade cannabis to a class C drug – in practice decriminalising its personal use – but this did not result in more drug use. Indeed, the official Home Office figures show a long-term decline in cannabis use in England and Wales among 16- to 24-year-olds, from 26% in 1996 reporting they had used it in the last year, to 16% in 2009-10. The "experiment" in decriminalisation between 2004 and 2009 (when cannabis was reclassified as a class B drug) did nothing to reverse this trend.